Some things in life are OK to skimp on. For instance, the beer you bring out when company arrives, economy-brand cleaners for your toilet, or even low-budget kitchen gadgets you’ll probably only use a few times anyways.

There are things in life you shouldn’t skimp on, however. My favourites are tires, sunglasses and sofas.

After a recent conversation with a friend who supervises automaker warranty claims for a living, I’ve got another one, too — any form of filter used by your car’s engine, and especially if that car is still under warranty.

My contact (who prefers not to be identified), showed me several photos, highlighting two recent incidents in which a customer saved a few dollars on their engine filters, but suffered thousands worth of damage in the process.

Both cases involved catastrophic engine damage, to the tune of nearly $10,000. Both cases were caused by use of improper filters and, therefore, were not covered by warranty.

Let me explain.

Customer number one gets their very first oil change — just 9,000 kilometres or so into the life of their new car — outside of the dealership setting. The factory oil filter is removed, and replaced, in the process. The replacement filter is an economy-branded filter from a local parts store, not a factory-approved unit from the automaker.

This low-budget oil filter, like most oil filters, has a rubber assembly inside that acts like a valve to help control how oil passes through it. Unfortunately, part of this rubber assembly became dislodged from the oil filter. The engine sucked it up, and moments later, it was blocking an oil passageway that provides cooling and lubrication to part of the engine’s cylinder head.

Starved of oil, this particular engine now had moments to live. Just a few seconds after the blockage, the engine’s valve timing hardware catastrophically failed, casting debris and engine oil into the engine combustion chambers. It looks like a bomb went off inside the engine.

Some of the resulting shrapnel was pushed into the nearby catalytic converter, destroying it. The catalytic converter? About $2,000. A new engine? About $8,000 more. Warranty coverage? Not a chance.

“Warranties don’t cover damage or wear caused by the use of non-factory parts, like this customer’s budget-brand oil filter. In fact, failure of any non-approved oil filter in this fashion would be met with the same result” my contact says.

There’s also customer number two. His vehicle is a bit older, but still under factory warranty.

Customer number two decides to change their engine air filter, which has the important task of filtering damaging particles and debris from every breath of air the engine inhales.

Thing is, they bought a non-approved air filter from the internet, and upon installing it, failed to realize it didn’t fit properly into the airbox.

With an opening around part of the filter, dirty air was allowed to bypass it altogether. Then, for months and months, this engine was inhaling air that contained bits of sand, dirt, pollen, bugs, and more.

This caused continual wear and damage to numerous parts of the engine before destroying it outright.

Warranty coverage? Nuked, and for the same reason.

“In this case, the customer was on the hook for about $7,000 in damage,” my contact explained. “And since the damage was caused by the use of a non-factory filter, it’s not covered by warranty, either.”

In both of the above cases, failure of a factory-approved filter would have been covered entirely.

“If it’s my filter that fails, even causing engine failure, then I’m covering it, because that’s our fault,” he says. “But warranty claims always involve finding a cause of the failure and if that failure was caused by user error, or non-approved parts, then the customer is probably in for a nasty surprise.”